Day9.scala

import scala.collection.mutable
object Day9 extends App {
  val preamble = 5
  val sampleArray: Array[Long] = Array(35, 20, 15, 25, 47, 40, 62, 55, 65, 95, 102, 117, 150, 182, 127, 219, 299, 277, 309, 576)
  
  findInvalidNumber(preamble, sampleArray)
  
  def findInvalidNumber(preamble:Int , sampleArray: Array[Long]) = {
    var firstIndex = 0
    var lastIndex = preamble
    val errorQueue = mutable.Queue[Long]().empty
    sampleArray.drop(preamble).foreach { number =>
      val set = mutable.HashSet[Long]().empty
      val slicedArray = sampleArray.slice(firstIndex, lastIndex).sorted
      val sumList = slicedArray.zipWithIndex.flatMap { n: (Long, Int) =>
        slicedArray.patch(n._2, Nil, 1).map(n._1 + _)
      }
      set ++= sumList
      if (!set.contains(number)) {
        errorQueue.addOne(number)
      }
      firstIndex += 1
      lastIndex += 1
    }
    println(errorQueue.mkString(","))
    errorQueue.front
  }
}